Variable valve timing system

A variable valve timing system for an engine in which a cylinder head on a cylinder is suspended on a vehicle body frame, the variable valve timing system comprising:

• an intake side camshaft and an exhaust side camshaft disposed on the cylinder head;
• and
• a variable valve device attached to one end portion of the intake side camshaft, wherein
• in a side view of a vehicle, when a side where the intake side camshaft is disposed is defined as an intake side of the cylinder head, and a side where the exhaust side camshaft is disposed is defined as an exhaust side of the cylinder head, in accommodating walls of the cylinder head which cover the intake side camshaft and the exhaust side camshaft from a side, the accommodating wall on the exhaust side is positioned more inward in a vehicle width direction than the accommodating wall on the intake side,
• a first bolt for fixing the intake side of the cylinder head to the cylinder is disposed more inward in the vehicle width direction than the accommodating wall on the intake side, and
• a second bolt for fixing the exhaust side of the cylinder head to the cylinder is disposed more outward in the vehicle width direction than the accommodating wall on the exhaust side.